Weird Internets is a series in which we spotlight and explore funny, bizarre, or otherwise interesting corners of the internet. Today, we talk to Alejandra Gaitan, whose cleavage-baring videos as "TheReplyGirl" have turned her into one of YouTube's most hated personalities.

"There's the brain, and there's a part in the brain called the hypothalamus," says Alejandra Gaitan. She's sitting in what looks like a bare bedroom in this video — beige wall, patterned bedsheet — wearing a low-cut blue blouse. The top half of her face is cut off so that her chest is the center of the shot. She has a thick accent and a slight tendency to ramble. "The hypothalamus controls all of your basic instincts, and with that comes the instinct of reproduction, and with the instinct of reproduction comes horniness, so, yeah."

Gaitan, a 24-year-old Canadian, is a "Reply Girl." In fact, she's literally The Reply Girl. Gaitan is more or less the first of an increasing number of young women to devote an entire YouTube channel to expertly-tagged videos of herself in somewhat revealing clothing, "reviewing" popular YouTube shows and viral videos and counting on the prominently-featured cleavage in her video's thumbnail to bring her, and her advertisers, an enormous audience. I'd contacted Gaitan — through YouTube, of course — after reading Fruzsina Eördögh's piece in the Daily Dot about the controversy that had sprung up around her, and watching this short YouTube documentary about her. I was fascinated with the way she'd managed to make a lot of money — not to mention a lot of enemies — using nothing but a webcam, several deep v-neck shirts, and an instinctive feeling for what makes both YouTube and the human brain work.

"The hypothalamus controls all of your basic instincts, and with that comes the instinct of reproduction, and with the instinct of reproduction comes horniness, so, yeah."

She made this particular video to answer a question I'd sent her about the way she dresses for her work. She plans on publishing it when this piece goes live on Gawker. "It's just the way the human brain works," she says. "Sex appeal just works. And denying the fact is just going against the basics of how we are all, how our brain works. Companies have made millions with sex appeal."

Gaitan hasn't made millions, exactly. "I had been below the poverty line for the longest while — at least seven years — and, you know what, I just wanted to make money on my own," Gaitan says in another video she prepared in response to my questions. "I was really desperate... Youtube was my salvation somewhat." She probably earns around a hundred dollars for most of her videos; the really popular ones — 500,000 hits and over — could net her close to $1,000. (A clause in the YouTube monetization contract prevents Gaitain from saying exactly how much she earns.) "It's a decent amount of money. Am I a millionaire? No. Not at all," she says. "If I had all the money in the world I probably wouldn't be freezing here in winter in Canada. I would most likely be somewhere in a tropical island."

Gaitan's ability to attract an audience — her hypothalamus-engine optimization — isn't unprecedented. Using your thumbnails to promise sex, regardless of the content of your videos, is a time-honored tradition on YouTube. But where your standard "YouTube porn fakeout" is often accidental and usually unrepeatable, reply girls have industrialized the business of sexy YouTube thumbnails. They've set up their own channels and monetization agreements. They produce and control their images and content. And they've turned a profit by intelligently, and ruthlessly, exploiting YouTube's own sharing mechanisms and algorithms.

She reels off a list of common reactions: "go kill yourself, go suicide, jump off a cliff, I'm going rape you, I'm going to go ahead kill you, I'm going to hack your account, etc, etc, etc, mainly negative."

Since the site's inception, YouTube users have "replied" to videos by making videos of their own. Sometimes it's to share similar content (you might reply to a cat video with another cat video, for example) but more often it's to share opinions. As on the rest of the internet, there is a surfeit of deeply-held beliefs on YouTube: any video that gets more than a few thousand views can expect a reply or two, no matter its content. A few years ago, YouTube itself, noticing the primitive attempts of its user base to communicate with one another, codified the reply system by weighing replies more heavily in the algorithm that determines what appears in the "related videos" section — and by adding a new section, above the comments, called "video responses."

This change is now the foundation of Gaitan's business. Working quickly to create her short, rambling, usually pointless videos — she makes between five and ten a day — she copies the original video's tags and secures herself a spot on its page. Her shirts do the heavy lifting of bringing people to the video, and then a quirk in YouTube's "related videos" algorithm kicks in: when viewers register their dislike of Gaitan's video en masse with the "thumbs down" button, it actually drives the video further up the "related videos" ranking. This makes sense — if the Speaker of the House makes a reply to President Obama, Democrats will hit "dislike," but his video is still a legitimate reply — but it can allow for deeply-hated videos to climb to prominent placement.

And people do hate her videos. Despite their high view counts, they receive among the most negative feedback on YouTube, whether you measure by "dislikes" or by the invective in the comment section. It's partly a function of the videos themselves, which tend to be more noise than signal, but it's hard to shake the feeling that some of the anger is directed at an undelivered promise of sex — or, at least, boobs. She reels off a list of common reactions: "go kill yourself, go suicide, jump off a cliff, I'm going rape you, I'm going to go ahead kill you, I'm going to hack your account, etc, etc, etc, mainly negative." On her Google Plus account, someone named Daniel Kelliher has commented on every single one of her posts with a single word: "Whore."

It's also about lost revenue. Most YouTube channels and shows rely on the "related videos" algorithm and the "reply video" section to direct viewers to other episodes of their shows. If Gaitan replies to a video made by the video game review series Yogscast (and she does, often, since those videos are so popular) and if people click on her thumbnail over Yogscast's (and they do), Yogscast loses viewers.

"There's a trend happening on YouTube right now which is basically just a bunch of fat-titty girls making stupid-ass reply videos to everything that comes out."

That's why channels are hitting back. Yogscast publicly complained on its website, and has been talking to YouTube about their problem. Other YouTubers have created their own video responses to the reply girl phenomenon. Complaining about reply girls has become something of a micro-industry itself — some of the anti-reply girl videos get hundreds of thousands of views, and the one seen here will likely hit a million views soon. (To an outsider, it can be difficult to distinguish between the initial videos, the reply-girl replies, and the third-party responses: videos from all stages of the controversy are to varying degrees amateurish, difficult to follow, unfunny, and more or less worthless.)

Gaitan has fans, too. "Regardless of all the hate, there's this small group that supports me," Gaitan says. "If the YouTube partnership or monetization program didn't exist, I would keep doing personal blogs, you know, 'cause they do appreciate me." She may have to switch to personal video blogs soon, as YouTube is reportedly changing its "related videos" algorithm to better account for reply girls. This isn't uncommon for the site: as Slacktory's Nick Douglas notes, "a lot of policy and tech changes came from dealing with people trying to game the system," a natural result of "a platform that rewards popular content but also rides on instant, repeated discovery."

Gaitan is changing her business practice to account for her newfound infamy — she's started a new series called "Kill the Reply Girl," inspired by the threats she's received, in which she acts out a death every day — but she's looking to transition out of the reply game entirely sometime soon.

"I hope that in the future I eventually can focus on personal blogs," she says. "That is something I enjoy a lot more than doing replies."

Vital Stats

INTERNETTING SINCE: Gaitan has been blogging for a while, but TheReplyGirl channel has existed for nearly a year, and is either the first or second "reply girl." She explains: "There is this channel called Megan Lee Heart... When I realized what she was doing, I said, 'wow this is genius.' It's not driving traffic from her subscribers but from YouTube. Me, I've been working on this account for a year now and, you know, I'm not a partner, so why not try it? So I opened a channel called The Reply Girl's Reviews which was originally my video review channel. Then, moving on, I opened The Reply Girl, which was a personal channel, and I opened The Reply Girl first, before Megan Speaks. But Meagan Speaks started doing reviews first, in the Megan Lee Heart channel. So, yeah.. The Reply Girl was out there before Megan Speaks, but Megan Speaks started doing video reviews in her Megan Lee Heart channel."

BEST KNOWN FOR: One of her videos, "re: Facebook Parenting: For the troubled teen.," racked up 1,480,728 views. (It received 1,964 likes and 14,341 dislikes.)

FAVORITE INTERNET THING: "I like it when I stumble upon funny videos... there was this video I reviewed not long ago of a kid that was talking about his toys. Now, the kid is like 2 years old; he cannot pronounce words well, so he said 'pussy' — it was supposed to be 'Percy' — so the kid said 'pussy, pussy,' so that was really really funny. I do like the videos. Some of the videos that I review I find them really good... There's this girl I've helped a lot that's called nelliereviews and she's a very cool, very nice girl. I really do wish her the best of luck; I wish her the best success in the world, and, you know what, I like to help reviewers who are just starting, because, in my opinion, YouTube is a place for everybody. It's not, like, only me, only me, only I can do reviews. That's what I think."

[thanks to Maeve Kierans and Maya Schwayder]